Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Summary of Activity Related to DSUs (Detail)

v3.8.0.1
Stock Based Compensation - Summary of Activity Related to DSUs (Detail)
12 Months Ended
Dec. 31, 2017
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of Options, Outstanding | shares 2,052,223
DSUs granted | shares 1,253,085
DSUs forfeited | shares 249,928
DSUs vested | shares (781,055)
Number of Options, Outstanding | shares 2,274,325
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares $ 11.58
Weighted Average Grant Date Fair Value, DSUs granted | $ / shares 15.81
Weighted Average Grant Date Fair Value, DSUs forfeited | $ / shares 12.63
Weighted Average Grant Date Fair Value, DSUs vested | $ / shares 11.53
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares $ 13.75
Deferred Stock Units [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of Options, Outstanding | shares 14,953
DSUs granted | shares 0
DSUs forfeited | shares 0
DSUs vested | shares (14,953)
Number of Options, Outstanding | shares  
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares $ 8.36
Weighted Average Grant Date Fair Value, DSUs granted | $ / shares 0
Weighted Average Grant Date Fair Value, DSUs forfeited | $ / shares 0
Weighted Average Grant Date Fair Value, DSUs vested | $ / shares $ 8.36
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares